Africanized honey bee response to differences in reward frequency

Abstract

Differences in predation pressure and floral resources exist among the endemic ranges of Apis mellifera subspecies. Those environmental differences should select for heterogeneity in forager flower fidelity among honey bee subspecies, particularly when reward frequency differences are associated with competing flower types. We tested that evolutionary model by examining the foraging behaviour of Africanized honey bees (AHB), and by comparing our observations with those recorded for Italian (A. m. ligustica) and Caucasian honey bees (A. m. caucasica). The response of AHB (A. m. scutellata hybrid/introgressant) to reward frequency differences among flower colours was examined using artificial flower patches. Each patch contained blue, white, and yellow flowers. When rewards offered by ail three flower-morphs were identical, some foragers restricted visitation to blue and white flowers, while others showed fidelity to yellow flowers. Bees visiting blue and white flowers did not show a preference for either the blue or white colour morph under those conditions. However, forager behaviour changed when they were presented with different reward frequencies associated with the alternative flower colours. Bees frequenting blue and white flowers favoured blue when it offered a reward more frequently than white, and favoured white when the reverse was true. That behaviour occurred not only when the more frequently rewarding flower colour offered a higher harvest rate, but also when harvest rates obtained from all flower colours were equal. A change in flower colour fidelity involving yellow vs. blue and white flowers was observed only when reward frequency difference was linked to maximizing harvest rate. Those results contrast sharply to reported A. m. ligustica and A. m. caucasica honey bee behaviour: neither Italian nor Caucasian bees respond to reward frequency differences among flower colours, even between blue and white flowers.